DESCRIPTION (Verbatim from the Applicant's Abstract): Colorectal carcinoma is the third most commonly diagnosed cancer and the second leading cause of death from cancer in the United States. Often it is diagnosed at an advanced stage, after the patient has developed symptoms, explaining its high mortality rate. Since most cancers arise from polyps over a 5 to 15 year period of malignant transformation, screening programs to detect small polyps less than 1 cm in diameter have been advocated. Unfortunately most people do not follow this recommendations. The health relatedness of this project is to dramatically increase the number of people willing to participate in screening programs by using a convenient, nearly risk-free procedure. Virtual colonoscopy is a new procedure in which computed tomographic images of the patient's abdomen are taken and a computer visualization system is used to virtually navigate within a constructed 3-D model of the colon. The broad, long-term objective of this proposal is to develop virtual colonoscopy as an accurate7 costeffective, non-invasive, comfortable technique to screen large segments of the population. To further advance this technology, the specific aims of this proposal are: (1) to develop electronic colon cleansing using bowel preparation methods and computer segmentation techniques, (2) to investigate means for generating a flight-path and a navigation environment, and correcting colon collapse, (3) to optimize automatic, real-time volume rendering with various interactive controls for analysis of suspected abnormalities, and (4) to determine the accuracy of virtual colonoscopy compared to optical colonoscopy. The research design and methodology will include evaluating the ability to electronically clean the colon in normal, college-aged volunteers by looking at virtual colonoscopy procedures performed on consecutive days; the feasibility of bringing the technology to a readily accessible environment by documenting the processing speed and quality of produced navigation through the colon; and the accuracy of real-time volume-rendering algorithms by comparing virtual and optical colonoscopy polyp detection in the same patient using a modified colon preparation with stool/fluid labeling oral contrast solutions.